YouTube misinformation

[Gary34]

This is one of the more misleading videos I’ve seen on YouTube. He’s not purposely being misleading I don’t think. I wouldn’t doubt if that video causes a few newbies to buy black AVTs. https://youtu.be/KjizFsQkgW4?si=1CyPlRxxIuz6fVii. There’s a bunch of misconceptions all throughout the video.

[Aya_Rei]

Thanks for the warning, sucks this sort of stuff keeps on happening. When I first saw the thread title I thought this was going to a video posted on the 'Video Capture Guides' channel, thankfully it wasn't. To me those channel's videos, or at least the videos that weren't originally from Reasonably British, are a breath of fresh air from all the misinformation spewing channels and people recommending extremely crappy setups, sucks that TechTVUSA is yelling about DV in their comment section, so the craptastic conversion train ain't stopping any time soon thanks to people like him.

[Gary34]

Reasonably British is funny. Video Capture Guides is good too. I expect things to be wrong in most every YouTube video that talks about VHS digitizing methods but sometimes it suprises me how off they are.

[aramkolt]

The problem is that there aren't well established sets of tests to prove that any individual frame TBC works appropriately, since most models are quite old and used, most people won't really know if what they have works as well as it theoretically could or if it works as well as it did when it was new.

In my opinion, the best evidence of a TBC working would be zero dropped frames on capture, no audio sync issues on long captures, and no visible image noise added. However, many people don't use a process that report dropped frames accurately or at all. A frame inserted that occurs at highly regular intervals, like every 3000 frames or so I think is ok as it probably represents a slight difference in the clock of the TBC compared to the capture software.

Another suggested TBC test would be the "VCR Blue Screen Test" - in other words that it can pass a blue screen from a VCR menu screen to the capture card. However, not all perfectly working TBCs pass this test. The Brighteye75 (BE75), for example, does not pass the Blue Screen Test (at least with NTSC VCRs), but is considered by the few that have them to be one of the best. Oddly, the BE5, and BE25 do pass that test, those just don't have an S-Video input unfortunately. The blue screen on a VCR actually isn't an NTSC compliant signal and is actually something like 288p and not 525/480i, though this can vary from VCR to VCR and this is why some TBCs don't recognize it as a legitimate signal to lock onto and pass.

I think the best way to test for addition of image noise would be to use a pattern generator run through the TBC and look at the output on a vectorscope/waveform monitor and see if there's a less clear waveform than without the passthrough. Most probably aren't going to invest in that equipment, so it's kind of subjective without that.

But back to that video - the main flaw there is probably that you can't get back to the interlaced content which you'd want if the hardware deinterlacer there (Up/Down/Cross Converter) happens to suck or if there are better deinterlacing methods that arise later. It also is reducing the frame/field rate presumably. Kind of looks like he's capturing from a DVD which is a bit disingenuous (reason I say that is he shows the frame rate to be 23.98 which is more of a DVD frame rate and is neither PAL or NTSC, though could be that he has the up/down/cross converter set to output at that frame rate). Would have been kind of interesting to see the HDMI DVD capture compared to his analog capture from the same DVD player. My guess is the analog capture looks much worse.

Doing hardware deinterlacing does save some steps later and may be more Mac-Friendly, you just have to realize it could be highly inferior to software deinterlacing and you won't really get an archive of the original format which may or may not matter to you.

In his setup, there's no way to tell if there are any dropped frames anyway because the analog to digital conversion step in the SDI to analog converter won't report dropped frames. If you had a specific video that was time-coded with a unique time code on each field/frame that was visible, you could check after the fact whether frames were dropped or inserted I suppose, but I haven't seen anyone really do that. It'd be way too time consuming to actually look through each frame to verify unless AI would have a way of pointing it out maybe, or perhaps to only look at the time codes on "rough" areas of video that have visual disturbances?

[traal]

You can use the "subtract" method explained in this post to detect where VirtualDub or the TBC has replaced dropped frames with duplicates of the last good one. Just hold down the right arrow key and watch for blank frames where they shouldn't be.

[NJRoadfan]

The VCR "blue screen" test is actually a test of how well a device tolerates 240p video (technically out of spec). A good capture card or TBC doesn't care and just digitizes it as 480i video like just about every flat panel TV does. I have a capture card here that is so strict, that it doesn't detect any input at all when the VCR's blue screen is showing or from period video game consoles.

All "infinite window" TBCs (technically what a full frame TBC is) will occasionally drop or add a frame to keep in sync with the input signal/audio due to clock drift or playback dropouts. It is impossible to avoid. Over the course of a 2 hour tape, this generally adds up to a few extra frames, but even in the linear tape editing days, this rarely caused any major issues (that and nobody played a tape continuous for 2 hours during editing). To detect this, you would need tapes with time code information recorded onto them.

As for the video above, his setup is very complicated. Just capture the SDI video direct!

[lordsmurf]

Quote:

Originally Posted by NJRoadfan

All "infinite window" TBCs (technically what a full frame TBC is)

I've sometimes noticed there's some disagreement on the term "infinite window" among older video users.

It's always been my understanding that "infinite window" refers specifically to field TBCs (ie, Panasonic AG-1980P) because of "infinite lines" being buffered by RAM that exceeds lines per field. Line TBCs came first, then field, then frame, because that's how RAM progressed in the 80s-90s (ie, larger and cheaper over time).

However, even now, there is really no way for RAM to exceed the frames (ie, the entire video, all frames). So it's not an infinite frame window.

Technically, I guess full-frame is "infinite field" (all 2 of them?), thus an "infinite window" of sorts. But that wasn't the intended use of the term.

As I always state, TBC is a wide term, multiple definitions can exist (including wrong/inaccurate definitions), so defining terms if often needed in context of video discussions.

I discussed this here in more detail last year at VH:

Quote:

Originally Posted by lordsmurf

Quote:

Nope.

Read it again:

Quote:

That refers to a whole field.

You can have "infinite lines" (aka whole field) without dumping RAM buffer, but you can't have "infinite frames" without dumping the RAM buffer.

and that Studio1 (SignVideo) article, since now gone:

Quote:

TBCs vs. Frame Synchronizers

Prior to the availability of digital video mixers, any two video sources mixed together through a video switcher had to be synchronously matched by using a time-base corrector if the video source was a playback VCR or a genlock-able camera if the video source was a live camera. It was necessary to match the scan rate of these video sources so that the transition took place during the vertical interval blanking period, the analog “non picture” that takes place between video fields. As you might have guessed, this was a very expensive process considering that you needed a TBC for each playback VCR and mid to high-end video cameras with genlocking capabilities.

When digital video mixers came into the picture, no pun intended, any non-synchronized video source could be plugged in and mixed, wiped or keyed with another non-synchronized video source (i.e. consumer VCRs and camcorders, laser-disk players, TV tuners, NTSC computer outputs).

A frame synchronizer literally takes a digital “snapshot” of each incoming frame of video and releases immediately as the next frame comes in. Once converted to the digital world, the video frame can be blended with any other digitized video frame via transitional effects.

Now, how does the frame synchronizer in your digital mixer differ from an actual time-base corrector? They both work on the principle of converting incoming video from analog to digital. And they both stabilize the video picture so that their respective outputs can feed other equipment requiring digitally-stable signals, such as the NewTek Video Toaster.

A time-base corrector, or TBC does one job: It corrects inconsistencies of an analog playback VCR. It accomplishes this by sampling one video scan line at a time (not an entire frame), corrects any instability by stripping the scan line of it’s old sync signal and replacing it with a brand new sync signal created by the TBC’s own built-in precise timing clock. Modern day TBCs, with their vast digital memory, can correct up to an entire field (262.5 scan lines) of incoming video. These are known as “infinite window” TBCs (obviously more effective than the two line correction capability of some “TBCs” built into high-end consumer VCRs).

The frame synchronizer, on the other hand, digitally synchronizes two separate video sources without necessarily correcting them.

There are some TBCs that have built-in frame synchronizers and there are frame synchronizers with built-in TBCs (i.e. Videonics MX-1). However, they are still two different creatures performing similar jobs.

Due to the digital video mixer’s ability to feed the Video Toaster a myth began that the Panasonic digital mixers have “secret” or “hidden” time-base correctors built in to them. The only thing a Video Toaster requires from an input is that it is digitally stabilized. And both TBCs and frame synchronizers accomplish that task. (Plus, as competitive as the digital mixer manufacturers are, if one of their digital mixers had a built-in TBC, the consumer would be the first to know about it.)